# Explain how the skin of a frog functions as a gas exchange surface.

> IB DP Biology Standard Level (2023 syllabus) — B3.1 Gas exchange · Explain · 4 marks

> Frogs are amphibians that can exchange gases across their skin as well as through their lungs. Cutaneous respiration accounts for a significant proportion of total gas exchange, particularly when the frog is at rest or submerged in water.

## Mark scheme (4 marks)

1. The skin is thin / has a thin epithelium, reducing the diffusion distance for gases
2. The skin must remain moist / covered in a mucus layer so that gases dissolve before diffusing across the membrane
3. A dense network of capillaries lies close to the skin surface, maintaining a steep concentration gradient for diffusion
4. The large surface area of the skin relative to body volume provides a sufficiently large area for gas exchange to meet metabolic demands

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-skin-of-a-68a48b4e) · Published by Druglandscape Ltd.